Artificial leather produced by the conventional production method, i.e., suitable for a common artificial leather sheet, is widely used for clothing, shoes, gloves and the like because it has a superior appearance and touch. However, it is inferior in strength and has too high an elongation. This makes it difficult to use the sheet to cover furniture, as a cover sheet for a car chair, for men's clothing and the like which require a form-stability.
To solve such a problem, there was proposed a method for improving form-stability by increasing the amount of polyurethane resin to be impregnated when producing the sheet for artificial leather. In this case, the artificial leather achieves excellent form-stability but is low in softness and accordingly, there is a risk that the appearance of the artificial leather becomes spoiled.
There was an attempt to decrease the amount of polyurethane resin to be impregnated to thus improve the appearance and touch of the product when producing a sheet for artificial leather. In this case, however, the form-stability of the artificial leather became degraded.
Japanese Patent Laid-Open No. S62-78281 and U.S. Pat. No. 5,256,429 disclose a composite sheet for artificial leather which is produced by inserting a layer of fabrics woven from a yarn having more than 1 denier into a non-woven fabric layer of an ultra fine fiber as a reinforcing material, needle-punching them and physically coupling the ultra fine fiber of the non-woven fabric layer and the yarns of the layer of the fabrics.
This method can improve the form-stability of the artificial leather but there is a problem that the fibers of the layer of the fabrics for reinforcement, which has a much large denier than the ultra fine fiber are raised and protrude to the surface of the composite sheet, thus making the touch of the artificial leather rough and hard. Additionally, when performing dyeing, there occurs a difference in dyeing concentration due to a difference in denier between the ultra fine fiber which protrudes to the surface and the thick fiber of the layer of the fabrics for reinforcement, thereby degrading the appearance of the product.
As seen from the conventional art, a composite sheet for artificial leather capable of improving the form-stability and touch of the artificial leather has not yet been developed.